A. Field of the Invention
This invention relates to power chip resistors. More specifically the invention relates to an improved power chip resistor with increased power dissipation in a small package.
B. Problems in the Art
Power resistors, chip resistors, and power chip resistors have numerous applications in electronic circuits including limiting current. The problem of limiting current or otherwise using a power chip resistor is sometimes in conflict with the amount of board space that can be allocated for the resistor. In order to increase the power dissipation of a chip resistor, the size of the resistor is increased. As electronic devices continue to decrease in size, board space and the need to reduce board space increases. Thus there is a problem in using a power chip resistor when there is limited board space.
Some attempts have been made at stacking chip resistors. A stacked chip resistor would reduce the amount of board space required as the size of the resistor would increase vertically. These attempts have created additional problems.
One such problem is that these attempts have used epoxy or other resins or polymers as an adhesive to physically connect each chip resistor in the stack. Epoxy is widely used as an adhesive in the art but has certain qualities that make it ineffective for stacking power chip resistors. In particular, long term use of epoxy or other polymers in a power chip resistor may result in an electrical instability effect over time due to the effects of resistive heating.
Another problem relates to the use of solder at the terminals of a stacked chip resistor. The magnitude of the resistive heating can be so great, particularly in high wattage power chip resistors, that when stacked, the solder melts. Because solder would melt, the power chip resistor would not be compatible with standard manufacturing practices and methods concerning population of components on a circuit board. In particular, standard flowing processes could not be used as the power chip resistor would not be flow solderable. Thus any accommodation of a power chip resistor into a circuit design would involve additional manufacturing costs.
It is therefore an objective of the present invention to provide an apparatus and method of making a power chip resistor that improves upon the state of the art.
It is a further objective of the present invention to provide a power chip resistor and method of making a power chip resistor that permits a power chip resistor to be made that requires reduced circuit board space.
It is a further objective of the present invention to provide a power chip resistor and method of making a power chip resistor that provide the capability of increased power dissipation.
It is a further objective of the present invention to provide a power chip resistor and method of making a power chip resistor that provide for stacking power chip resistors.
It is a further objective of the present invention to provide a power chip resistor and method of making a power chip resistor that provides for a resistor with a higher power rating.
It is a further objective of the present invention to provide a power chip resistor capable of use at high voltages.
It is a further objective of the present invention to provide a power chip resistor that may be surface mounted.
It is a further objective of the present invention to provide a power chip resistor that is stable over time.
It is a further objective of the present invention to provide a power chip resistor that does not melt a solder connection.
It is a further objective of the present invention to provide a power chip resistor that uses a thick film resistant element.
It is a further objective of the present invention to provide a power chip resistor that is flow solderable.
It is a further objective of the present invention to provide a power chip resistor that reduces manufacturing costs.
These and other objectives will become apparent from the following description.